Rotary pump with pressure relief

ABSTRACT

A rotary pump includes a housing, rotors, an inlet chamber, an outlet chamber and pressure relief means. The pressure relief means includes a movable wall normally resiliently biased into engagement with one of said rotors and exposed to fluid pressure at said outlet chamber. At a predetermined maximum pressure, the fluid pressure force acting upon the wall will overcome the resilient bias and move the wall away from said rotors to a degree sufficient to interconnect said outlet and said inlet chambers in fluid communication and allow fluid to flow therebetween and thereby disrupt the pumping action of the rotors. The movable wall pressure relief contacts only one of the rotors.

0 United States Patent [151 3,655,299 Connelly [4 Apr. 11, 1972 [5ROTARY PUMP WITH PRESSURE Primary Examiner-Carlton R. Croyle RELIEFAssistant Examiner-Richard J. Sher Attorn Tea 0 and Todd [72] Inventor:Laverne R. Connelly, Marshall, Mich. ey gn y [73] Assignee: EatonCorporation, Cleveland, Ohio [57] ABSTRACT [22] Filed. No 12 1970 Arotary pump includes a housing, rotors, an inlet chamber, an outletchamber and pressure relief means. The pressure relief [21] Appl. No:88,790 means includes a movable wall normally resiliently biased intoengagement with one of said rotors and exposed to fluid pressure at saidoutlet chamber. At a predetermined maximum (g! "417/313; pressure thefluid pressure force acting upon the wall will overcome the resilientbias and move the wall away from said [58] Field ofSearch ..4l7/283.310, 4l8/l32 rotors to a degree sufficiem to interconnect said outletand said inlet chambers in fluid communication and allow fluid to [56]References Cned flow therebetweenand thereby disrupt the pumping actionof UNITED STATES PATENTS the rotors. The movable wall pressure reliefcontacts only one of the rotors. 2,405,061 7/1946 Shaw ..4l8/l32 12Claims, 9 Drawing Figures FLUID PRE$SURE\ L soft; 277:? 19), DE

IOI I02 I03 REACTION FORCE=PRESSURE X AREA I0! I02 I03 IIIIIIIIIII IBIASING FORCE l4 REACTION FORCE=PRESSURE X AREA 6 I'm IIIII II AINVENTOR 30| 302 303 304 305 LAVER/VE R. CON/VELLY A TTORNEYS ROTARYPUMP WITH PRESSURE RELIEF BACKGROUND OF INVENTION 1. Field of InventionThe present invention relates to a pressure relief for a rotary pump,and more particularly, to a pressure relief of the sliding wall typewherein the resiliently biased, slidable wall is in fluid communicationwith the pumping chambers of the pump.

2. Discussion of the Prior Art It has been necessary to provide rotarypumps of the type having inner and outer rotors with eccentric axes forrotation, such as those used in lubrication pumps for internalcombustion engines, with an effective pressure relief valve. For thosepumps utilized as lubrication pumps, the pressure differentials betweenrunning and shut-off pressure is often quite small, 105 p.s.i. runningpressure with l psi. shut-off pressure. For those pumps, a verysensitive pressure relief valve must be provided.

Heretofore, pressure relief valves of the sliding wall type have beeninadequate for pumps wherein sensitivities of the magnitude mentionedabove were required. For this reason, sliding wall valves with the costadvantage thereof, were usable only in those applications having arelatively large on-off pressure differential.

SUMMARY OF INVENTION The present invention provides a more sensitivesliding wall type pressure relief than heretofore possible, by providingmeans whereby the wall contacts only one of a pair of rotors. Bycontacting only one of the rotors an increased surface area of slidablewall is exposed to the generated pump pressure and thus the generatedfluid force acting on the wall, namely that force which equals theexposed slidable wall area times pressure, will be proportionallyincreased. Thus, for any given pressure a force signal of greatermagnitude is generated, allowing applicants pressure relief to becapable of much more sensitive operation than has heretofor beenpossible with sliding wall pressure relief devices.

The biasing force on the wall is sufficient to permit the pump togenerate fluid pressure up to a predetermined, desirable maximumpressure, at which point the fluid pressure force on the wall willovercome the bias and said wall will be moved away from the rotors tothe extent that the pumping chambers are put into fluid communicationwith each other so that the fluid flows between the outlet chamber andthe inlet chamber thereby disrupting the pumping action of the rotorsbeyond the predetermined pressure. As the fluid pressure drops to anacceptable level, the biasing force will again urge the movable wallinto a position whereby the outlet and inlet chambers of the pump areagain sealed from each other and normal pumping will resume.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of ahydraulic pump, illustrating certain features of the present invention.

FIG. 2 is a cross-sectional view taken along the line 2-2 of FIG. 1.

FIG. 3 is a cross-sectional view of a hydraulic pump illustrating analternate embodiment of the present invention.

FIG. 4 is a partial, cross-sectional view of an alternate embodiment ofthe present invention.

FIG. 5 is a plane view of one element of FIG. 4.

FIG. 6 is a cross-sectional view of the pump of FIG. 1 in a secondoperating condition.

FIG. 6a is a force diagram illustrating the hydraulic forces acting on acertain portion of the pump of FIG. 1.

FIG. 7 is a cross-sectional view illustrating a prior art device.

FIG. 7a is a force diagram illustrating the hydraulic forces acting on acertain portion of the pump of FIG. 7.

DETAILED DESCRIPTION OF INVENTION Referring now more specifically to thedrawings and more specially to FIGS. 1 and 2, a rotary pump maygenerally be seen at 10. The pump 10 includes a housing 12 with a fluidinlet 14 and fluid outlet 15. Housing 12 has a cylindrical cavity 16defined by cylindrical wall 18 and wall 20 which is transverse to theaxis 22 of said cylindrical cavity 16. As is wellknown in the art, portscommunicating with low pressure inlet 14 and high pressure fluid outlet15 are formed in the upper wall 20.

Mounted for eccentric rotation within cavity 16 is an outer rotor 30having teeth 32 inter-engaged with teeth 34 of an inner rotor 36. Itwill be noted that axis 38 of inner rotor 36 is parallel to and off-setfrom axis 22 of outer rotor 30. The parallel but off-set axis ofrotation results in eccentric rotational pumping action as is well-knownin the art when inner rotor 36 is driven and may be more fullyunderstood by reference to US. Pat. No. 2,792,788. Fixedly mounted toinner rotor 36 is a rotary shaft 39 which is provided with splines 42for attachment to an external driving means (not shown).

Sealing the opposite end of cavity 16 is a slidable wall 40 which ismovable, under certain conditions, along axis 22 while maintaining itssealing relation to cylindrical wall 18. Mounted to housing 12 by a snapring 42 is a resilient biasing means 44 which resiliently urges wall 40in a generally upwards direction in FIG. 1. The present resilientbiasing means 44 has the embodiment of a Belleville spring.

Wall 40 is formed with a raised boss 46 which will contact the lower endof rotor 36 when said wall is resiliently urged into upward position. Itshould be noted that due to raised boss 46, a lower surface 48 of wall40 will not in any position contact outer rotor 30. A clearance 50 isthus formed between surface 48 and the lower end of outer rotor 30 whichclearance is of the magnitude of 0.0005 inch which due to the effect ofhydrostatic filling will not adversely affect the normal pumping actionof rotary pump 10.

Reference to FIG. 3 will indicate a modified form of rotary pump 110wherein a flat slidable wall 140 is utilized with an elongated innerrotor 136. The effect is identical with that described in the aboveparagraph, with a clearance 50' of the magnitude of 0.0005 inch beingformed between the outer rotor 130 and slidable wall 140. As theoperation of pumps 10 and 110 are identical the operation of pump 110will not be described in detail.

FIGS. 4 and 5 illustrate a further modification of the presentinvention. In FIGS. 4 and 5 a modified Belleville spring 60 is provided.Modified Belleville spring 60 has a radial slot 62 and two small holes64 adjacent the radial slot. Utilizing a tool,

such as the well-known snap-ring pliers, the holes 64 may be forcedcloser together, thus decreasing the outer diameter of spring 60 so asto permit insertion thereof into the cavity 16 and retention thereof inthe cavity 16 by cooperation of the spring 60 with a groove 69 in thewall 18. Thus, the modified Belleville spring 60 may be utilized as aself-mounting fastening device to retain the movable wall 240 in thecavity 16 and to resiliently bias the movable wall 240 into engagementwith the inner rotor 236 thereby eliminating the need for snap rings orother means of retaining the resilient biasing means in place.

The operation ofpumps 10, and 210 of FIGS. 1, 3 and 5 respectively isidentical and therefore will be described in detail for pump 10 only. Inoperation, fluid enters pump 10 through inlet 14 from which it iscommunicated through the inlet port in upper wall 20 to a pumpingchamber 70. Pumping chamber 70 is formed by teeth 32 and 34 of inner andouter rotors 30 and 36 respectively together with the upper wall 20 andslidable wall 40. As shaft 39 is rotated in either direction, thechamber 70 is rotated toward outlet 15 and is reduced in size; and thefluid entrapped therein is forced under pressure out the high pressureoutlet 15. When pump 10 is generating fluid pressures below thepredetermined maximum, biasing means 44 is sufficient to urge slidablewall 40, upward into contact with inner rotor 36 and maintain clearance50 at a magnitude so as not to interfere with the pumping action. As thegenerated fluid pressure exceeds a predetermined maximum, the generatedpressure force acting upon surface 48 will overcome resilient biasingspring 44 and wall 40 will move away from rotors 30 and 36. As is seenin FIG. 6, this will create an enlarged clearance 50' between wall 40and outer rotor 30 and a clearance 150 between the inner rotor 36 andthe raised boss 46. The clearances 50 and 150 will allow fluid to flowfrom chamber to chamber and effectively destroy the pumping and pressurecreating action of the eccentrically rotating rotors. As the pressuredrops to an acceptable level, the slidable wall 40 will be urged upwardby resilient means 44 towards the rotors, and clearances 50' and 150will be closed allowing pumping action to resume.

For comparative purposes, FIG. 7 will illustrate a prior art device 310in which slidable wall 340 contacts both inner rotor 346 and outer rotor330. The upper surface of wall 340 has been divided into surfaces 301,302, 303, 304 and 305 for illustrative purposes.

It should be noted, the reaction force generated by the fluid pressure,of that force which will tend to overcome the bias, is equal togenerated fluid pressure times wall area in contact with the fluid. Itmay easily be seen by reference to FIGS. 6a and 7a that the area of thepresent invention in contact with fluid pressure, namely 101 and 103,far exceeds that contact area of the prior art device, namely 302 and304. Thus, for any given generated fluid pressure, the resultinggenerated reaction force will be greater in the present invention thanin the prior art device. By increasing the force generated by any givenpressure it is possible to design a pressure relief sensitive to smallerincrements of pressure differentials.

Applicants novel arrangement of slidable wall 40 and rotors 30 and 36has the effect of amplifying the pressure relief reaction to any givenpressure differential.

it should also be noted that the clearance 50' required to crack thepumping chambers and allow fluid to flow between the rotors is partiallyformed by the gap 50. Therefore, the movable wall has a lesser distanceto move away from the rotors to effect a pressure relief and thus has afaster response than the prior art devices.

By providing a sliding wall type pressure relief that has a largerreaction to a given pressure than does the prior art devices, applicanthas invented'a more sensitive, quicker acting and therefore more usabledevice than has been heretofore available.

Having thus described my invention, I now claim:

1. A rotary pump comprising:

a housing having a cylindrical cavity therein;

inner and outer rotors with inter-engaging teeth forming pumpingchambers mounted for eccentric rotational motion within said cavity;

a slidable wall sealing one side of said cavity, said'wall beingslidable in an axial direction of said cavity and forming a wall forsaid pumping chambers when said wall is within a predetermined axialdistance of said rotors;

resilient biasing means mounted to said housing for resiliently urgingsaid slidable wall into engagement with only one of said rotors, saidbiasing means permitting said slidable wall to move a distance greaterthan the predeten mined axial distance away from said rotors when saidpump generates a pressure greater than a predetermined maximum. 2. Therotary pump of claim 1 wherein said resilient biasing means is aBelleville spring.

3. The rotary pump of claim 2 wherein said Belleville spring has oneradial slot and at least one hole proximate each side of said slot.

4. The rotary pump of claim 1 wherein said resilient biasing means is aC-shaped Belleville spring including means permitting gripping of saidBelleville spring and tangentially compression thereof.

5. The rotary pump of claim 1 wherein only the inner rotor is contactedby said slidable wall.

6. The rotary pump of claim 1 wherein said slidable wall is formed witha substantially centrally located raised boss so as to contact the innerrotor only.

7. The rotary pump of claim 1 wherein said inner rotor extends to aposition beyond said outer rotor so as said slidable wall will contactsaid inner rotor only.

8. A rotary pump comprising:

a housing having a substantially cylindrical cavity therein;

inner and outer rotors having inter-engaging teeth forming the sidewalls of pumping chambers mounted for eccentric rotation within saidcavity;

a slidable wall sealing one end of said cavity, said slidable walladditionally forming one wall of said pumping chambers when saidslidable wall is within a predetermined distance of said rotors, saidslidable wall being formed so as to contact only one of said rotors; and

a resilient biasing means mounted in said housing for resiliently urgingsaid slidable wall in a direction towards said rotors, into anengagement with said one of said rotors and to within a predetermineddistance of the other of said rotors, said biasing means allowing saidslidable wall to move a distance greater than the predetermined distancefrom said rotors when said pump generates greater than a predeterminedmaximum pressure.

9. A rotary pump comprising:

a housing having a substantially cylindrical cavity containingeccentrically rotating inner and outer rotors;

a wall slidable within and sealing one end of said cavity, said wallinteracting with said rotors to form pumping ch'ambers when said wall islocated within a predetermined axial distance of one of said rotors andin contact with the other of said rotors: and

biasing means mounted to said housing for locating said wall within thepredetermined axial distance from said one of said rotors and biasingsaid wall into engagement with the other of said rotors provided thepump generated pressure does not exceed a predetermined maximumpressure.

10. The combination of claim 9 wherein said wall is formed with acentrally raised boss.

11. The combination of claim 9 wherein the inner rotor is longer thanthe outer rotor, thereby exposing a larger area of said wall to pumpgenerated pressure.

12. The combination of claim 9 wherein said biasing means is a C-shaped,self-retaining Belleville spring.

1. A rotary pump comprising: a housing having a cylindrical cavitytherein; inner and outer rotors with inter-engaging teeth formingpumping chambers mounted for eccentric rotational motion within saidcavity; a slidable wall sealing one side of said cavity, said wall beingslidable in an axial direction Of said cavity and forming a wall forsaid pumping chambers when said wall is within a predetermined axialdistance of said rotors; resilient biasing means mounted to said housingfor resiliently urging said slidable wall into engagement with only oneof said rotors, said biasing means permitting said slidable wall to movea distance greater than the predetermined axial distance away from saidrotors when said pump generates a pressure greater than a predeterminedmaximum.
 2. The rotary pump of claim 1 wherein said resilient biasingmeans is a Belleville spring.
 3. The rotary pump of claim 2 wherein saidBelleville spring has one radial slot and at least one hole proximateeach side of said slot.
 4. The rotary pump of claim 1 wherein saidresilient biasing means is a C-shaped Belleville spring including meanspermitting gripping of said Belleville spring and tangentiallycompression thereof.
 5. The rotary pump of claim 1 wherein only theinner rotor is contacted by said slidable wall.
 6. The rotary pump ofclaim 1 wherein said slidable wall is formed with a substantiallycentrally located raised boss so as to contact the inner rotor only. 7.The rotary pump of claim 1 wherein said inner rotor extends to aposition beyond said outer rotor so as said slidable wall will contactsaid inner rotor only.
 8. A rotary pump comprising: a housing having asubstantially cylindrical cavity therein; inner and outer rotors havinginter-engaging teeth forming the side walls of pumping chambers mountedfor eccentric rotation within said cavity; a slidable wall sealing oneend of said cavity, said slidable wall additionally forming one wall ofsaid pumping chambers when said slidable wall is within a predetermineddistance of said rotors, said slidable wall being formed so as tocontact only one of said rotors; and a resilient biasing means mountedin said housing for resiliently urging said slidable wall in a directiontowards said rotors, into an engagement with said one of said rotors andto within a predetermined distance of the other of said rotors, saidbiasing means allowing said slidable wall to move a distance greaterthan the predetermined distance from said rotors when said pumpgenerates greater than a predetermined maximum pressure.
 9. A rotarypump comprising: a housing having a substantially cylindrical cavitycontaining eccentrically rotating inner and outer rotors; a wallslidable within and sealing one end of said cavity, said wallinteracting with said rotors to form pumping chambers when said wall islocated within a predetermined axial distance of one of said rotors andin contact with the other of said rotors: and biasing means mounted tosaid housing for locating said wall within the predetermined axialdistance from said one of said rotors and biasing said wall intoengagement with the other of said rotors provided the pump generatedpressure does not exceed a predetermined maximum pressure.
 10. Thecombination of claim 9 wherein said wall is formed with a centrallyraised boss.
 11. The combination of claim 9 wherein the inner rotor islonger than the outer rotor, thereby exposing a larger area of said wallto pump generated pressure.
 12. The combination of claim 9 wherein saidbiasing means is a C-shaped, self-retaining Belleville spring.